© 2020 Author(s). Saudi Arabia has the world's fifth-largest desert and is the biggest importer of food and agricultural products. Understanding soil microbial communities is key to improving the agricultural potential of the region. Therefore, soil microbial communities of the semiarid region of Abha, known for agriculture, and arid regions of Hafar Al Batin and Muzahmiya were studied using Illumina sequencing. The results show that the microbial communities of the Saudi desert were characterized by the presence of high numbers of Actinobacteria, Proteobacteria, and Firmicutes. In addition to Sahara desert signature phyla like Gemmatimonadetes, biogeochemically important microorganisms like primary producers, nitrogen fixers and ammonia oxidizers were also present. The composition of the microbial community varied greatly among the sites sampled. The highest diversity was found in the rhizospheric soil of Muzahmiya followed by Abha. Firmicutes, Proteobacteria and Actinobacteria were the three main phyla detected in all the samples. Soils from the agricultural region of Abha were significantly different from other samples in containing only 1% Firmicutes and 3-6 times higher population of Actinobacteria and Bacteroidetes, respectively. The presence of photosynthetic bacteria, ammonia oxidizers, and nitrogen fixers along with bacteria capable of surviving on simple and unlikely carbon sources like dimethylformamide was indicative of their survival strategies under harsh environmental conditions in the arid soil. Functional inference using PICRUSt analysis shows an abundance of genes involved in photosynthesis and nitrogen fixation.